The present invention relates to the generation of patient-specific implants based on the examination findings on a patient obtained by imaging methods in medical technology.
It has been possible for long to use, to a limited degree, exogenic material (implants) to close organ defects. The recent state of art is to generate hard-tissue implants specifically adapted to a patient either by obtaining the implants during a surgical operation under use of existing intermediate models or, more recently, under use of CAD/CAM technologies as an aid in computer-aided reconstruction. Imaging methods of the medical technology, such as computer tomography, nuclear magnetic resonance tomography, and sonography increasingly form the basis for generation.
It is common medical practice (refer to, for example, U.S. Pat. No. 4,097,935 and U.S. Pat. No. 4,976,737) to use as implants plastic and workable, respectively, metal webs and metal plates, easily to form materials that have a short curing time (for example, synthetic resin) and endogenic material from the patient by which the defects are closed during the surgical operation, i.e. the implant is obtained during the operation, formed and adapted to the defect. However, metallic implants such as webs and plates etc. can be very disturbing at later diagnosises on the patient and can even render impossible to carry out future special methods of examination, in particular, when larger defect areas are concerned. The progress of operation is usually dependent on the situation of treatment itself, and the experience of the surgeon. In such cases it is scarcely possible to have a specific operation planning for the insertion of the implant in advance. Therefore the operated on patient occasionally has to undergo follow-up treatments that are an additional physical and psychological strain for the patient. Moreover, some materials, such as synthetic materials which are easily to form and/or can be produced at comparatively low expenditures, can only be utilized in a limited degree with respect to their loadability and endurance. Additionally, there is the desire of the patient to get an aesthetic appearance which in many cases is very hard to realize.
Furthermore, “Stereolithographic biomodelling in cranio-maxillofacial surgery, a prospective trial”, Journal of Cranio-Maxillofacial Surgery, 27, 1999 or U.S. Pat. No. 5,370,692 or U.S. Pat. No. 5,452,407 or U.S. Pat. No. 5,741,215), it is possible to start the design of the implant by generating a physical three-dimensional intermediate model, for example, by stereolithographic methods based on medical imaging methods mentioned at the beginning. Then the implant is manually modeled in the defect site by use of plastic workable materials and only then the implant is finally manufactured from the implant material. Thereby the implant preferably is produced from materials of a higher strength, such as titanium.
Furthermore, there is known (“Schädelimplantate—computergestützte Konstruktion und Fertigung”, Spektrum der Wissenschaft, Februar 1999; “Die Rekonstruktion kaniofazialer Knochendefekte mit individuellen Titanimplantaten”, Deutsches Ärzteblatt, September 1997), to generate a simple three-dimensional CAD patient model from the data obtained by applying imaging methods on a patient, and to use these data to manually design the implant by computer under use of simple design engineering methods. Subsequently the implant is manufactured for the surgical operation by a computer numeric control (CNC) process.
The methods mentioned hereinbefore, however, have the common disadvantage that the result of the implant-modelling predominantly depends on the experience, the faculty and the “artistic” mastership of the person generating respectively producing said implant. The manufacturing, starting from the data obtained and up to the operationally applicable and mating implant, requires high expenditures of time and cost which are still increased when there is manufactured a so-called intermediate model. The manufacture of an implant during an operation requires correspondingly high expenditures of time and executive routine for the surgical intervention and, thus, means a very high physical and psychological strain, last not least for the patient. Moreover, it is still more difficult to operatively and form-fittingly insert an implant, non-mating to the defect site on the patient, while attending to medical and aesthetic aspects. Also here the special skill and experience of the surgeon very often will be decisive for the outcome of the operation. Practically and in the frame of the clinical routine, the first-mentioned methods can only be used with narrow and/or lowly structurized defects and they will very soon reach their technological limits with complicated defects and implants as concerns shaping and fitting.
The operative expenditure is greatly dependent on the adaptability of the implant to the defect site. But with a manufacture of an implant via intermediate models this precision can be additionally deteriorated due to copying the intermediate model.
In complicated cases the implants have to be manufactured in lengthy and extremely time-consuming processes and, if necessary, via a plurality of intermediate stages. Within this comparatively long period the defect area on the patient can possibly change in the meantime. These changes, in practice, cannot be sufficiently taken into consideration as concerns the adaptability of the implants and additionally increase the operation expenditures.
From the viewpoint of the surgeon as well as of the patient it will be desirable that the implants should be manufactured in the shortest possible time, also with respect to the surgical intervention, and with a high adaptability to the defect site on the patient. Concrete information not only about the defect site on the patient but also to the size and shape of the implant to be inserted should be available to the attending surgeon for planning the operation in advance and before the intervention on the patient.